Similarly, people have consistently always dramatically reacted to the better video quality of people using DSLR regardless of the max video resolution a video chat outputs.
If you have a ton of depth and big lens, you are going to get a properly lit image with the right lighting, and lets face it, if you go through the motions of setting up a DSLR for streaming you aren't going to be "that person" sitting on the couch with the laptop on the coffee table aiming up at your backlit silhouette.
My iMac (2010) had a better low light image @480p than the 2019 MBA purely due to physical size.
A more functional-oriented-shaped-chassis for such a Macbook Pro has plenty of space for a high-end 4K Dolby Vision HDR front-facing camera.
Even the iMac doesn't have a "high end" camera despite the additional depth, but its at least on Par with $100 external webcams
You would need at least 7-8mm lid thickness to include anything on par (with currently released tech) or MUCH thicker if you want "high end".
An extra 4mm of dead air in the rear of the screen would be very wasteful of space if the only improvement to the lid is the camera when:
a) People who use DSLR's and GoPro's will Still use DSLR's and GoPro's
b) So many decent external options exist.
c) People insist on using worst-case lighting (A camera needs light people)
A great high def 4k camera is not going to be a dealbreaker for the majority of people. And an
acceptable image on par with the iMac or iPhone will be the best we can hope for when they can miniaturize without sacrificing low light performance.